As to online sources, I do not know. My friend is a missionary who learned the language more than 20 years ago, and his son grew up with the language and got his degree in linguistics. My recommnedation is that you pursue a search on Indo-European linguistics. Perhaps a university would be able to help you. I know that Middlebury College (VT) has a linguistics department; parhaps they could direct you to some relevant textbooks which you could purchase second-hand. I'm sure they have a website in which you could track down and email a professor in that field to ask.

Stand Fast, Craigellachie!